Mobile communication system in which communication resources are allocated based on traffic congestion

ABSTRACT

Each mobile station is accommodated in a base station through a radio transmission path. A base station control device controls each base station. A mobile station is accommodated in a first base station. Each of the base stations notifies the mobile station of the condition of the communication resources of the base station, respectively. If the mobile station judges that it is advantageous to be accommodated in a second base station instead of the first base station, the mobile station makes a request for hand-off to the base station control device. The base station control device issues a hand-off command to both of the first and second base stations. Then, the mobile station is accommodated in the second base station.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a divisional of U.S. application Ser. No. 10/373,494filed on Feb. 21, 2003, now U.S. Pat. No. 7,260,398, which is acontinuation application of an International Application ofPCT/JP00/06448, which was filed on Sep. 20, 2000, the contents of whichare herein wholly incorporated by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a mobile communication system and inparticular, relates to a mobile communication system adopting CDMA.

2. Description of the Related Art

Recently, mobile communications have widely spread. In a mobilecommunication system, each mobile station is accommodated in the nearestbase station and is connected to a network through the base station. Inthis case, since each base station accommodates as many subscribers aspossible, usually radio signals are multiplexed when transmitted. Forthe multiplex method of radio signals, conventionally,Frequency-Division Multiple Access (FDMA) or Time-Division MultipleAccess (TDMA) is adopted. However, in the next generation system,Code-Division Multiple Access (CDMA) is anticipated to becomemainstream.

In CDMA, each channel is identified by a code. Specifically, whentransmitting a signal, a transmitter (mobile station or base station)spreads the spectrum of the signal by multiplying the signal by aspecific code. Then, a receiver (base station or mobile station) decodesthe signal by multiplying an incoming signal by the same code as thatused by the transmitter. Therefore, in CDMA, a specific frequency bandis shared by a plurality of channels.

In a mobile communication system, generally, hand-off (or hand-over) isperformed. Hand-off means to change the base station accommodating amobile station from a source base station to a target base station whenthe mobile station accommodated in a specific base station (the sourcebase station) travels to the communications area of another base station(the target base station). In this case, whether hand-off should beperformed is decided, for example, based on the power of an incomingradio signal at the mobile station. In this case, if the power of asignal from the source base station at the mobile station drops below aspecific threshold value and simultaneously if the power of a signalfrom the target base station exceeds a specific threshold value,hand-off is performed.

Although currently a mobile communication system is mainly used forvoice communications, it is predicted that the amount of datacommunications will become high in the future. Voice communications areconducted at low and most often constant speed, while datacommunications are conducted at high and variable speed. Therefore, if ahand-off method presuming voice communications is adopted in a mobilecommunication system mainly used for data communication, there is apossibility that a variety of inconveniences may occur. In addition, ifa communication resource management method presuming voicecommunications is adopted in a mobile communication system mainly usedfor data communication, there is a possibility that communicationresources will not be efficiently used.

However, neither a detailed hand-off method for data communications(packet data communications and the like) nor a detailed communicationresource management method for data communications have been proposed.In particular, such methods have not been proposed in a mobilecommunication system adopting CDMA.

SUMMARY OF THE INVENTION

An object of the present invention is to provide both a hand-off methodand a communication resource management method in a mobile communicationsystem taking data communications into consideration.

The mobile communication system of the present invention comprises: afirst base station accommodating a mobile station through a radiotransmission path; a second base station communicative with the mobilestation through a radio transmission path; and a judgment unit forjudging whether to perform hand-off, based on the usage of thecommunication resources of the first and second base stations.

In this system, whether to perform hand-off is determined based on theusage of the communication resources of each base station. Specifically,a base station for accommodating the mobile station is determined basedon the usage of the communication resources of each base station.Therefore, the mobile station is accommodated, for example, in the basestation that can provide the most communication resources and high-speedcommunications becomes available accordingly.

The mobile communication system in another aspect of the presentinvention is provided with a base station accommodating a plurality ofmobile stations, the mobile communication system comprises: a detectionunit for detecting a call originating from a mobile station accommodatedin the base station; an acquisition unit for obtaining communicationresources to be allocated to the call; and a rate adjustment unit forreducing the data rate of another mobile station communicating throughthe base station if the communications resource to be allocated to thecall cannot be obtained.

In this system, when a certain mobile station originates a call, thedata rate of another mobile station is reduced if necessary. In thisway, communication resources to be allocated to the mobile station whichoriginates the call can be secured. The data rate of another mobilestation can not only be adjusted using a call originating from a certainmobile station as a trigger, but it can also be increased when the callof a certain mobile station is released. Alternatively, when there isdelay in communications of a certain mobile station, the data rate ofthe mobile station can be improved.

In the mobile communication system in another aspect of the presentinvention, a mobile station and a base station are connected via a radiotransmission path, and the base station and a base station controldevice are connected via a transmission line. The mobile communicationsystem comprises: a notification unit for periodically notifying thebase station control device of the usage of the communication resourcesof the radio transmission path from the base station; a determinationunit for determining the communications resource of a radio transmissionpath and the communications resource of a transmission line to beallocated to the mobile station based on the notice; and an allocationunit for allocating the communications resource of the radiotransmission path and the communications resource of the transmissionline to the mobile station based on the determination.

In this system, the usage of the communication resources of the radiotransmission path to be managed by the based station is periodicallyinformed to the base station control device. Therefore, the base stationcontrol device can allocate transmission line resources corresponding tothe radio resources that the base station can allocate to the mobilestation to the mobile station. In this way, radio resources andtransmission line resources are never maintained unbalanced and theineffective use of communication resources can be avoided.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 shows the configuration of the mobile communication system of thepresent invention.

FIG. 2 shows communication resources managed by the base station andbase station control device.

FIG. 3 shows an example of a transmitting power management table.

FIG. 4 shows an example of a modulator management table.

FIG. 5 shows an example of a spreading code management table.

FIG. 6 shows an example of a demodulator management table.

FIG. 7 shows an example of a decoder management table.

FIG. 8A shows an example of a frame-offset management table.

FIG. 8B shows an example of a band management table.

FIG. 9 is a sequence chart showing a process for a mobile stationjudging whether to perform hand-off.

FIG. 10 is a flowchart showing a process for judging whether to requesthand-off.

FIG. 11 is a sequence chart showing a process for a base station controldevice judging whether to perform hand-off.

FIG. 12 is another sequence chart showing a process for a base stationcontrol device judging whether to perform hand-off.

FIG. 13 is a sequence chart showing a process for adjusting data ratewhen a new call is established.

FIG. 14 is a sequence chart showing a process for adjusting data ratewhen a call is released.

FIG. 15 is a sequence chart showing a process for adjusting data ratewhen there is delay in an upstream transmission line.

FIG. 16 is a sequence chart showing a process for adjusting data ratewhen there is delay in a downstream transmission line.

FIGS. 17 through 20 show specific examples of the rate adjustment methodof the mobile communication system in the second embodiment.

FIG. 21 shows the communications resource management of the mobilecommunication system in the third embodiment.

FIGS. 22 through 25 show sequence charts showing processes forallocating communication resources in the mobile communication system ofthe third embodiment.

FIGS. 26 through 29 show sequence charts showing processes for managingcommunication resources in the mobile communication system of the thirdembodiment.

DESCRIPTION OF THE PREFERRED EMBODIMENT First Embodiment

FIG. 1 shows the configuration of the mobile communication system of thepreferred embodiment. Note that FIG. 1 shows only devices directlyrelated to the present invention.

Mobile stations 1 through 3 are portable terminal devices, such as atelephone set, a PDA, a personal computer and the like. Each of themobile stations 1 through 3 comprises an interface establishing a radiotransmission path with one or more base stations and transmits/receivessignals to/from the base station through the radio transmission path.

Base stations 11 and 12 each comprise an interface establishing a radiotransmission path with each of the mobile stations 1 through 3 andaccommodates the mobile stations 1 through 3. Each of the base stations11 and 12 is connected to a base station control device 21 through atransmission line, and their operation is controlled by the base stationcontrol device 21. Here, although the transmission line is basically anoptical fiber cable, a metal cable or the like, it can be a radiotransmission path.

The base station control device 21 controls the base stations 11 and 12,and connects each base station to a network. The base station controldevice 21 is connected to an arbitrary switch 31 in the network.

In this way, each of the mobile stations 1 through 3 is connected to anetwork through the base station and the base station control device. Inother words, each of the mobile stations 1 through 3 is connected to anetwork through a radio transmission path and a transmission line. Inthis embodiment, signals are multiplexed using CDMA in a radiotransmission path and they are multiplexed using TDM in a transmissionline.

Next, the hand-off operation is described. In an existing mobilecommunication system, hand-off is performed, for example, when a mobilestation accommodated by a certain base station travels to thecommunications area of another base station. For example, in FIG. 1, ifthe mobile station 2 accommodated in the base station 11 travels to thecommunications area of the base station 12, the mobile station 2 cantransmit/receive signals to/from the base station 12. In this case, ifthe power of the radio signal from the base station 11 drops below athreshold value and simultaneously the power of the radio signal fromthe based station 12 exceeds a threshold value, hand-off is performed.Then, the mobile station 12 is accommodated by the base station 12 afterthat. In this way, in the existing system, whether to perform hand-offis judged based on the power of a radio signal.

However, in the system of the embodiment, whether to perform hand-off isjudged based on the following parameters:

-   1a: Level of a radio signal from a base station at a mobile station-   1b: Level of a radio signal from a mobile station at a base station-   2a: Quality of a radio transmission path for transmitting signals    from a base station to a mobile station-   2B: Quality of a radio transmission path for transmitting signals    from a mobile station to a base station-   3: Usage of communication resources managed by a base station and/or    a base station control device

In this case, each of the “Level” described in 1a and 1b can be obtainedby monitoring the amplitude or power of a radio signal. “Quality”described in 2a and 2b can be obtained by monitoring, for example, a biterror rate or frame error rate. The parameter 3 will be described indetail later.

Next, the concept of hand-off in the mobile communication system of theembodiment is described. In FIG. 1, it is assumed that the communicationarea of the base station 11 and that of the base station 12 overlap eachother and that the mobile station 2 can transmit/receive radio signalsto/from each of the base stations 11 and 12. It is also assumed that themobile station 2 is currently being accommodated in the base station 11.

In the situation described above, if many of the communication resourcesof the base station 11 are being used by other communications, thecommunication resources allocable to the mobile station 2 decreases. Forexample, as shown in FIG. 1, if the mobile station 1 being accommodatedin the base station 11 starts high-speed communications, thecommunication resources allocable to the mobile station 2 decreases. Inthis case, the mobile station 2 must, for example, reduce thetransmission speed.

In this case, it is assumed that there is much of availablecommunication resources left in the base station 12. That is to say, itis assumed that there are much of communication resources allocable tothe mobile station 2 left in the base station 12. In this case, in thesystem of this embodiment, hand-off is performed, and the mobile station2 becomes accommodated in the base station 12. Then, the mobile station2 can perform high-speed communications by using the communicationresources of the base station 12.

In this way, in the mobile communication system of this embodiment,whether to perform hand-off is decided based on the communicationresources (including the communication resources of a radio transmissionpath and those of a transmission line) of a base station. In this case,as a matter of fact, the power of an incoming radio signal is alsoconsidered. Instead of the power of the radio signal, the quality of aradio transmission path can also be considered. Alternatively, both thepower of the radio signal and the quality of a radio transmission pathcan be considered.

FIG. 2 shows communication resources managed by a base station and abase station control device. In FIG. 2, “F (forward)” and “R (reverse)”represent a direction from a network to a mobile station (downstreamdirection) and a direction from a mobile station to a network (upstreamdirection), respectively.

A “transmitting power” is a power used by a base station to transmit aradio signal to a mobile station. Here, a base station multiplexes andtransmits a plurality of signals. Therefore, the total transmittingpower of a base station is the sum of the respective transmitting powersof individual radio signals. However, the maximum total transmittingpower of a base station is predetermined, for example, by a variety ofregulations. Therefore, if a large transmitting power is allocated to acertain radio signal, there is only a small amount of transmitting powerleft to be allocated to another radio signal.

As well known, in CDMA, the transmitting power of a radio signal isproportional to the data rate (communications rate) of data beingtransmitted using the signal. In other words, although low speedcommunications require only a small amount of transmitting power,high-speed communications require a large amount of transmitting power.If a base station accommodates many mobile stations, the amount oftransmitting power allocable to a radio signal to be transmitted to eachmobile station becomes small. Therefore, the data rate to be allowed toeach mobile station becomes low. If the number of mobile stationsaccommodated in a base station is small, the amount of transmittingpower allocable to a radio signal to be transmitted to each mobilestation becomes large. Therefore, the data rate to be allowed to eachmobile station becomes high.

FIG. 3 shows a table used to manage the transmitting power of each radiosignal. This table stores information representing the data rate of eachof the signals transmitted using corresponding radio transmission path(or radio channel) between a base station and each mobile station, andinformation representing a transmitting power corresponding to the datarate. This table is used to determine the data rate of each radiochannel in such a way that the sum of the transmitting powers ofindividual radio signals does not exceed the maximum transmitting powerof a base station.

All signals transmitted from a base station are collectively amplifiedand are transmitted into the air. In this case, since a transmittingpower is needed in proportion to a transmitting rate in CDMA, high-speeddata cannot be transmitted if a power of a specific value or more is notallocated. However, since in a base station, the maximum totaltransmitting power is restricted by hardware, the total limited powermust be efficiently divided among a plurality of channels.

A “modulator” represents a modulator which is used to modulate signalsto be transmitted from a base station to a mobile station, and ismanaged by the modulator management table shown in FIG. 4. The number ofmodulators which can be provided in each base station is predetermined.This table stores information representing the usage (in use/available)of each modulator and if the relevant modulator is in use, it alsostores information identifying the radio channel using the modulator.

A modulator is needed for each communications channel. A plurality ofmodulators are sometimes needed in proportion to the speed depending onthe type of a modulator. When a plurality of modulators are needed in acase where many modulators are provided in an array, there is sometimesa restriction that only consecutively arrayed modulators can be used. Inparticular, if low-rate signals, such as voice and the like, areallocated here and there in the modulator array, a plurality of idlemodulators cannot be consecutively secured. Therefore, high-speed datacannot be allocated. In this case, since the number of modulators isphysically limited, the efficient management of modulators is needed.

A “spreading code” is used to spread signals transmitted between a basestation and a mobile station, and is managed by the spreading codemanagement table shown in FIG. 5. The number of available spreadingcodes of each base station is predetermined. This table storesinformation representing the usage (in use/available) of each spreadingcode and if the relevant spreading code is in use, it also storesinformation identifying the radio channel using the spreading code. Forthe spreading code, a Walsh code is used.

In a CDMA system, a Walsh function and the like are used for thespreading codes, and channels are identified by enabling Walsh codes tobe orthogonal to one another for each channel. The number of spreadingcodes is limited, and when allocating a spreading code to each channel,a remaining available code is allocated. The degree of a spreading code,which is required depending on the data rate, is variable. The higherthe data rate becomes, the smaller the degree of the spreading codebecomes. If a plurality of spreading codes are used here and there in ascattered manner, spreading codes cannot be allocated to high-data ratecommunications. Therefore, the efficient allocation of a spreading codeis also needed.

A “demodulator” represents a demodulator which is used to demodulatesignals transmitted from a mobile station to a base station, and ismanaged by the demodulator management table shown in FIG. 6. The numberof demodulators provided in each base station is basically the same asthe number of modulators. This table stores information represents theusage (in use/available) of each demodulator and also informationidentifying the radio channel using the demodulator if the relevantspreading code is in use.

A “decoder” represents a decoder which is used to decode signalstransmitted from a mobile station to a base station, and is managed bythe decoder management table shown in FIG. 7. The number of decodersprovided in each base station is predetermined. This table storesinformation represents the usage (in use/available) of each decoder andif the relevant decoder is in use, it also stores informationidentifying the radio channel using the decoder. For the decoder, forexample, a Viterbi decoder or a turbo-decoder is used.

A “frame-offset” is information used to designate a timing in which asignal should be inserted in a frame transmitted/received between a basestation and a base station control device. Specifically, for example,frame-offset designates a prescribed time slot in a TDM frame with aplurality of time slots. More specifically, frame-offset is, forexample, an offset in units of 1.25 ms obtained by dividing a 20 msframe transmitted/received between the base station and base stationcontrol device into 16 pieces. The frame-offset is managed by theframe-offset management table shown in FIG. 8A. In other words, a 2 Mbpsline connects the base station and the base station control device andthis line is managed in the unit of 20 ms frame, which is the basicframe size of a CDMA system. This 20 ms frame is divided into 16 pieces,and each channel allocation is managed in units of 1.25 ms. In thiscase, if channels are focused on a specific frame-offset, there is apossibility that all of the channels may not be accommodated. Therefore,when allocating a frame-offset to a new channel, the frame-offset mustbe allocated so as to be properly distributed, depending on a channelallocation situation for each frame offset.

A “channel ID” is information used to identify a channel established ina transmission line between a base station and a base station controldevice. Specifically, a channel ID is attached to identifytransmitted/received data. In other words, a number is attached to eachof a plurality of pieces of data transmitted/received in one call andthe data are managed inside the device and so on. Generally, theattached number and the piece of data are processed in pairs inside thedevice and, the length of the attached number is also limited.

A “band” is information represents a band allocated to each channelestablished in a transmission line between a base station and a basestation control device, and is managed by the band management tableshown in FIG. 8B. Specifically, the band is allocated to each channelthat is established in a frame in units of 1.25 ms transmitted/receivedbetween a base station and a base station control device. In this case,for example, a plurality of channels are allocated to one frame-offset.Therefore, the band of each channel must be managed in such a way thatthe frame can accommodate all the channels.

Since the throughput of an inter-device interface between a base stationand a base station control device is limited, the limited throughputmust be efficiently divided and used among subscribers. For example, ifan ATM line is used for the inter-device interface, the entire resourcesof an ATM cell transferred between devices are divided with reference tothe transmitting timing of data (frame-offset) and transmission band. Inthis case, the frame-offset and the band are managed together.

Next, the sequence of the hand-off of the present invention isdescribed. Both a case where a mobile station initiates the hand-off anda case where a base station initiates the hand-off are described below.

FIG. 9 is a sequence chart in the case where a mobile station judgeswhether to perform hand-off. In this description, a base stationaccommodating the mobile station is called a “source base station”. Inother words, it is assumed that the mobile station is currentlyconducting data communications through the source base station. A basestation having the possibility of accommodating the mobile station iscalled a “target base station”.

Each base station broadcasts resource information regularly or whenthere is a prescribed trigger. Here, a “prescribed trigger” means when acondition of the communication resources managed by a base stationchanges. For example, when a call is terminated, when a new call isestablished, when the data rate of arbitrary communications changes andthe like are all considered “prescribed triggers”. It is assumed thatresource information broadcast by each base station is informed to allmobile stations located within the communications area of the relevantbase station.

In this case, resource information informed from a base station to amobile station is information about the resources shown in FIG. 2.Specifically, such information is generated by referring to the tablesshown in FIGS. 3 through 8. For example, the difference between themaximum transmitting power of a base station and the currenttransmitting power (available power), a data rate corresponding to thedifference (allowable data rate) or the number of unit channels that canbe converted into the above two pieces of data are informed asinformation about the “transmitting power”. As for information about a“modulator”, a “spreading code”, a “demodulator”, a “decoder” and a“channel ID”, information indicating whether there is an availablemodulator, information indicating whether there is an availablespreading code, information indicating whether there is an availabledemodulator, information indicating whether there is an availabledecoder and information indicating whether there is an available channelID are inform, respectively. Furthermore, as for information about a“band”, for example, information indicating that there is an availableband is informed.

There is no need for resource information informed from a base stationto a mobile station to include all the pieces of information describedabove. However, it is preferable for this resource information toinclude at least information about transmission power.

Upon receipt of resource information from both the source base stationand the target base station, the mobile station judges whether torequest a hand-off, based on the two pieces of resource information. Ifit decides to request a hand-off, the mobile station issues a hand-offrequest to a base station control device through the source basestation. This judgment method will be described later.

Upon receipt of the hand-off request from the mobile station, the basestation control device issues a hand-off command to the source basestation, the target base station and the mobile station. In this case, ahand-off command including a command to disconnect a radio connection tothe mobile station is issued to the source base station. In addition, ahand-off command including a command to accommodate the mobile stationis issued to the target base station. Furthermore, a hand-off commandincluding a command to establish a radio connection between the mobilestation and target base station, and a command to disconnect the radiotransmission path between the mobile station and source base station isissued to the mobile station. Then, each of the source base station, thetarget base station and the mobile station returns a hand-off responsecorresponding to the hand-off command.

Then, each of the source base station, the target base station and themobile station performs a hand-off process according to the hand-offcommand. Specifically, for example, negotiations for channel allocationand the like are conducted between the mobile station and target basestation, and a radio transmission path is established. Then, the radiotransmission path between the mobile station and source base station isreleased. After that, the mobile station is accommodated in the targetbase station and is connected to a network through the target basestation.

Although in the example described above, each base station individuallybroadcasts resource information to the mobile station, resourceinformation can also be informed to the mobile station by anothermethod. For example, a base station may inform resource information tothe mobile station upon request from the mobile station.

FIG. 10 is a flowchart showing a process for judging whether to requesthand-off. A mobile station performs this process. It is assumed thatthis mobile station is accommodated in the source base station.

In step S1, the mobile station monitors the power of a radio signal froma target base station. In step S2, the mobile station checks whether thepower of the signal detected in step S1 exceeds a predeterminedthreshold value. If the power of the signal exceeds the threshold value,the mobile station performs processes in and after steps S3. Otherwise,the flow returns to step S1.

In step S3, the mobile station receives resource information from thesource base station. In step S4, the mobile station receives resourceinformation from the target base station.

In step S5, the mobile station checks whether there are availablecommunication resources in the target base station. Specifically, themobile station checks whether a radio channel can be established betweenthe mobile station and the target base station. More specifically, forexample, the mobile station refers to the resource information informedfrom the target base station and checks whether there is an availablemodulator, an available spreading code, an available demodulator, anavailable decoder and the like in the target base station. If there arenecessary available communication resources left in the target basestation, the flow proceeds to step S6. Otherwise, the process isterminated.

In step S6, the mobile station compares the resource informationreceived from the source base station with that received from the targetbase station. Specifically, the mobile station checks in which basestation there are more available resources, in the source base stationor target base station. For communication resources to be compared, forexample, transmitting power is used. In this case, for information abouttransmitting power, the available power or allowable data rate of eachbase station is used, as described above. Therefore, in this case, instep S6, the respective available powers or allowable data rates of thetwo base stations are compared, as described above.

If the available resources of the target base station is larger thanthat of the source base station, in step S7, the mobile stationgenerates the hand-off request and transmits the request to the basestation control device. This hand-off request includes, for example,information identifying each of the source base station and the targetbase station. If the available resources of the target base station issmaller than that of the source base station, the process is terminatedwithout generating a hand-off request.

In this way, in the mobile communication system of this embodiment, if amobile station can transmit/receive a radio signal to/from a pluralityof base stations (in this case, a source base station and a target basestation), hand-off is performed in such a way that the mobile stationcan be connected to a network through the base station with the mostavailable resources. After being accommodated in the base station withthe most available resources, the mobile station can conduct high-speedcommunications using as many communication resources as possible.

Although in this embodiment, available resources are compared, thepresent invention is not limited to this method. That is to say, forexample, a plurality of pieces of resource information received from aplurality of base stations may be compared, and a base station that cansecure the most communication resources can also be selected.

FIG. 11 is a sequence chart showing a process where a base stationcontrol device judges whether to perform a hand-off. It is assumed thatthe mobile station is currently conducting data communications through asource base station, as in the example shown in FIG. 9.

Each base station notifies a base station control device of resourceinformation periodically or when there is a prescribed trigger. Here,the prescribed trigger and resource information to be informed are thesame as those in the example described with reference to FIG. 9.

Upon receipt of resource information from both the source base stationand the target base station, the base station control device judgeswhether to perform a hand-off, based on the tow sets of resourceinformation. This judgment process is basically the same as the processof the mobile station shown in FIG. 10. However, in the base stationcontrol device, steps S1, S2 and S7 are not executed.

If it is judged that a hand-off should be performed, the base stationcontrol device issues a hand-off command to each of the source basestation, the target base station and the mobile station. These hand-offcommands are basically the same as those described with reference toFIG. 9. Then, each of the source base station, the target station andthe mobile station returns a hand-off response corresponding to therespective hand-off command to the base station control device.

Then, each of the source base station, the target station and the mobilestation performs a hand-off process according to the respective hand-offcommand described above, as in the sequence described with reference toFIG. 9. In this way, after this hand-off process, the mobile station isaccommodated in the target base station and is connected to a networkthrough the target base station. However, even if the hand-off commandis issued, a hand-off process is not performed when the power of a radiosignal received from the target base station by the mobile station islower than a threshold value or when the quality of the radiotransmission path between the mobile station and target base station islower than a prescribed level.

In this sequence, resource information can be managed by the switchstation or can be reciprocally informed between all the base stations.

FIG. 12 is another sequence chart showing a process for the base stationcontrol device judging whether to perform a hand-off. In this sequence,when detecting that the power of a radio signal from the target basestation exceeds a threshold value, the mobile station notifies a basestation control device of the fact. Upon receipt of this notice, thebase station control device makes a request for resource information toeach of the source base station and the target base station. On theother hand, each of the source and target base stations notifies thebase station control device of resource information, as requested. Then,the base station control device judges whether to perform hand-off,according to the two pieces of resource information. Since the procedureafter that is the same as that of the sequence shown in FIG. 9 or 11,the description is omitted.

In this way, in the mobile communication system of the first embodiment,if a mobile station can transmit/receive signals to/from a plurality ofbase stations, hand-off is performed in such a way that the mobilestation can be connected to a network through a base station with themost available communication resources of all the base stations.Therefore, the mobile station can always be accommodated in an optimalbase station and can conduct high-speed communications.

Second Embodiment

As described about the first embodiment, the maximum total transmittingpower of a base station is predetermined and the data rate of a signaltransmitted through a radio transmission path is also restrictedaccordingly. Therefore, for example, if high-speed packet datacommunications are attempted, the amount of communication resources thatcan be allocated to other communications become small, which affectsother communications. In packet data communications, the data ratechanges greatly. Therefore, if a large amount of communication resourcesis fixedly allocated to packet data communications, there arecommunication resources reserved without being used when the data rateof the packet data communications drops.

This problem can be solved if the amount of communication resources tobe allocated to each connection and/or the data rate of each connectionis dynamically adjusted, as requested.

In the mobile communication system according to the second embodiment,the allocation of communication resources or data rate is adjusted usingone of the following items as a trigger.

-   (1) Origination of a new call-   (2) Release of a call-   (3) Delay in a reverse link (upstream link)-   (4) Delay in a forward link (downstream link)-   (5) Inquiry

The “origination of a new call” is detected by a base stationaccommodating a mobile station that is about to start communications.When a new call is established, communication resources must beallocated to the new call. In this case, if there are availablecommunication resources, the communication resources are allocated tothe new call. However, if there are no available communicationresources, a part of communication resources already allocated to aspecific connection must be re-allocated to the new call. Therefore, inthis case, the data rate of the specific connection will be reduced.

The “release of a call” is detected by a base station accommodating themobile station when communications are terminated. If a call isreleased, communication resources which have been allocated to thereleased call can be re-allocated to another call. In this case, thedata rate of a specific connection can be improved by allocating thereleased communication resources to the specific connection.

A “delay in a reverse link” occurs when a sufficient data rate is notassigned to a connection for transmitting data from a mobile station toa base station. Specifically, the delay in a reverse line is detectedwhen the data from a mobile station are not transmitted to a basestation within a predetermined time period. The mobile station comprisesa data queue (for example, a FIFO memory) for temporarily storing datato be transmitted to a base station, and it is judged whether there isdelay based on whether there are data left in the data queue. If thereis the delay, the fact is informed to the base station control deviceand the data rate of a corresponding connection is improved using thisnotice as a trigger.

A “delay in a forwarding link” occurs when a sufficient data rate is notassigned to a connection for transmitting data from a base station orbase station control device to the mobile station. The base station orthe base station control device comprises a buffer memory fortemporarily storing data to be transmitted to the mobile station foreach connection, and it is detected that there is the delay when theamount of data stored in the buffer memory exceeds a threshold value. Ifthere is the delay in a specific connection, the data rate of thespecific connection will be improved.

An “inquiry” is a procedure where a base station control device makes aninquiry about resource information by polling to base stations. Ifavailable communication resources are found in this inquiry, the datarate of a specific connection will be improved by allocating theavailable communication resources to the specific connection.

A method for adjusting a data rate when the triggers (1) through (5)described above occurs is described with reference to FIGS. 13 through16 below.

FIG. 13 is a sequence chart showing a process for adjusting a data ratewhen a new call is established. In this example, it is assumed that themobile station 1 is currently conducting packet data communications at afull rate (the maximum transfer rate) through a base station 11. It isalso assumed that the mobile station 2 located within the communicationarea of the base station 11 has originated a call to start newcommunications in this state.

When detecting the new call, the base station 11 returns a responsemessage to the mobile station 2 and notifies a base station controldevice of the origination of a call. When detecting the origination of acall, the base station control device 21 issues a resource allocationrequest (1301) to the base station 11. This resource allocation request(1301) is an inquiry message on whether there are availablecommunication resources to be allocated to the new call left.

Upon receipt of the resource allocation request (1301), the base station11 checks whether there are any available communication resources to beallocated to the mobile station 2, by referring to the tables shown inFIGS. 3 through 8 and the like. In this example, it is assumed thatthere are no such available communication resources. In this case, thebase station 11 returns a resource-full response (1302) to the basestation control device 21. The resource-full response (1302) is amessage indicating that there are no available communication resources.If there are available communication resources, the communicationresources are allocated to the mobile station 2. In this case, thecommunications of the mobile station 1 are not affected.

Upon receipt of the resource-full response (1302), the base stationcontrol device 21 issues an adjustment instruction (1303) to the mobilestation 1. This adjustment instruction (1303) is a notificationindicating that the data rate should be adjusted from a “full rate” to a“½ rate”. The base station control device also issues a rate adjustmentrequest (1304) to the base station 11. This rate adjustment request(1304) is an instruction to adjust the data rate of the mobile station 1from a “full rate” to a “½ rate”. Although in the example shown in FIG.13, the rate adjustment request (1304) is issued after the adjustmentinstruction (1303) is issued, the rate adjustment request (1304) can beissued before the adjustment instruction (1303) is issued.

Each of the mobile station 1 and the base station 11 adjusts a data ratein a specific timing upon request from the base station control device21. After that, the mobile station 1 is connected to a network with a “½rate”. In this case, the base station 11 enables a part of thecommunication resources which have been allocated to the mobile station1 to be used for other communications. Specifically, transmitting powerwhich has been assigned to the mobile station 1 is reduced by reducingthe data rate of the mobile station 1, and the saved transmitting powercan be used for other communications.

Then, the base station control device 21 issues a resource allocationrequest (1305) to the base station 11. This resource allocation request(1305) includes an instruction to allocate available communicationresources to the mobile station 2. Then, the base station 11 returns aresponse to the base station control device 21 and properly allocatescommunication resources to the mobile station 2. In this way, the mobilestation 2 starts communications at a prescribed data rate.

Although in the example shown in FIG. 13, saved communication resourcesare allocated to the mobile station 2 by reducing the data rate of themobile station 1, communication resources can also be re-allocated bythe following methods. Specifically, some communication resources whichhave been allocated to the mobile station with the highest data rate ofa plurality of mobile stations accommodated in the base station 11 canbe re-allocated to a new call. Alternatively, if packet datacommunications and voice communications coexist, some communicationresources allocated to an arbitrary or all packet data communicationscan be re-allocated to a new call.

FIG. 14 is a sequence chart showing a process for adjusting the datarate when a call is released. In this example, it is assumed that mobilestations 1 and 2 are connected to a network through a base station 11.It is also assumed that the mobile station 1 is conducting packet datacommunications at a ½ rate. It is further assumed that the mobilestation 2 has terminated communications.

The mobile station 2 issues a call release request (1401) to the basestation control device 21. Upon receipt of this request, the basestation control device 21 returns a response message to the mobilestation 2 and issues a call release request (1402) to the base station11. The base station 11 disconnects the connection to the mobile station1 in response to this request and then returns a response message to thebase station control device 21.

Then, the base station control device 21 issues a resource releaserequest (1403) to the base station 11. This resource release request(1403) includes an instruction to release communication resources whichhave been allocated to the mobile station 2 and to use the releasedresources for other communications. Upon receipt of this resourcerelease request (1403), the base station 11 releases the communicationresources which have been allocated to the mobile station 2.

Then, the base station control device 21 issues a resource allocationrequest (1404) to the base station 11. This resource allocation request(1404) includes an inquiry message on whether there are availablecommunication resources sufficient to improve the data rate of themobile station 1. Then, the base station 11 refers to the tables shownin FIGS. 3 through 8 and the like in response to this resourceallocation request (1404) and notifies the base station control device21 of the state of available communication resources.

If there are available communication resources sufficient to improve thedata rate of the mobile station 1, the base station control device 21issues a rate adjustment request (1405) to the base station 11. Thisrate adjustment request (1405) is an instruction to adjust the data rateof the mobile station 1 from a “½ rate” to a “full rate”. If there areno available communication resources sufficient to improve the data rateof the mobile station 1, the base station control device 21 terminatesthe process without issuing the rate adjustment request (1405).

Furthermore, the base station control device 21 issues an adjustmentinstruction (1406) to the mobile station 1. This adjustment instruction(1406) is a notice indicating that a data rate should be adjusted fromthe “½ rate” to the “full rate”. As a result, the mobile station 1 isconnected to a network at the “full rate” through the base station 11.

FIG. 15 is a sequence chart showing a process for adjusting a data ratewhen there is delay in an upstream transmission line. In this example,it is assumed that a mobile station 1 is connected to a network at a ½rate through the base station 11.

The base station control device 21 makes an inquiry about whether thereis delay, to the mobile station 1. The mobile station 1 comprises a dataqueue for temporarily storing data to be transmitted to the base station11, it judges whether there is delay based on whether there are data inthe data queue left. Alternatively, whether there is delay is judgedbased on whether all pieces of data stored in the data queue aretransmitted to the base station 11 within a prescribed time period whenthe mobile station 1 receives the inquiry from the base station controldevice 21. Then, the mobile station 1 notifies the base station controldevice 21 of the judgment result using an inquiry response (1501).

The sequence after the fact that there is delay in the mobile station 1is informed to the base station control device 21 is the same as thatdescribed with reference to FIG. 14. Specifically, the base stationcontrol device 21 issues a resource allocation request (1502) and a rateadjustment request (1503) to the base station 11. Then, the base station11 allocates available communication resources to the mobile station 1.In addition, the base station control device 21 also issues anadjustment request (1504) to the mobile station 1. In this way, themobile station 1 is connected to a network at the “full rate” throughthe base station 11.

Although in the example shown in FIG. 15, the mobile station 1 notifiesthe base station control device 21 of the occurrence/non-occurrence ofdelay upon inquiry from the base station control device 21, theoccurrence/non-occurrence of delay can also be spontaneously informed tothe base station control device 21 when a delay occurs. In this case,the mobile station 1 issues a resource allocation request to the basestation control device 21 instead of the inquiry response (1501).

FIG. 16 is a sequence chart showing a process for adjusting a data ratewhen there is delay in a downstream transmission line. In this example,it is assumed that a mobile station 1 is connected to a network at a ½rate through a base station 11.

The base station control device 21 comprises a buffer memory fortemporarily storing data to be transmitted to the mobile station 1. Ifthe amount of data stored in the buffer memory exceeds a thresholdvalue, the base station control device 21 judges that there is delay ina connection to the mobile station 1.

The process after the delay is detected is the same as that describedwith reference to FIG. 14. Specifically, the base station control device21 issues the resource allocation request and the rate adjustmentrequest to a base station 11. Then, the base station 11 allocatesavailable communication resources to the mobile station 1. The basestation control device 21 issues the adjustment instruction to themobile station 1. In this way, the mobile station 1 is connected to anetwork at full rate through the base station 11.

Although in the example shown in FIG. 16, a buffer memory is provided inthe base station control device 21, it can also be provided in the basestation 11. In this case, for example, the base station control device21 makes an inquiry about an amount of data stored in the buffer memoryto the base station 11 and judges whether to adjust the data rate of themobile station 1, based on the result.

FIGS. 17 through 20 show specific examples of a rate adjustmentprocedure in the mobile communication system of the second embodiment.In this example, it is assumed that packet data communications and voicecommunications coexist. In FIGS. 17 through 20, P1-P6 and V1-V37represent packet data communications and voice communications,respectively. A base station (and a base station control device)properly allocates limited communication resources among packet datacommunications and voice communications. In this example, a power (thetransmitting power of a radio signal transmitted by a base station), adevice (modem device for a signal transmitted/received to/from a mobilestation in a base station), a code (spreading code for spreading signalstransmitted/received between a mobile station and a base station) and aline (time slot in TDM communications between a base station and a basestation control device) are taken as communication resources.

A fundamental channel (F channel) or supplementary channel (S channel)is allocated to each connection. In this case, the amount of resourcesallocated to a fundamental channel is the same as that of a voicechannel. In packet data communications, a fundamental channel isallocated to a connection for the packet data communications, and whenthe amount of data being transmitted increases, a supplementary channelcan be allocated. In this case, the amount of resources of thesupplementary channel is variable as in the sequence shown above.

If there are available communication resources left when a newconnection is established, the available communication resources areallocated to the new connection. In this case, the maximum possiblecommunication resources can be allocated to packet data communications.In the example shown in FIG. 17, the full rate of a supplementarychannel is allocated to each of packet data communication connectionsP1, p2 and p3.

If there are no available communication resources left when a newconnection is established, some communication resources which have beenallocated to a specific connection will be allocated to the newconnection by reducing the data rate of the specific connectionaccording to the sequence shown in FIG. 13. In the example shown in FIG.18, the data rate of a packet data communication connection P1 isreduced from a “full rate” to a “½ rate” in order to establish a voicecommunication connection V6. Here, communication resources obtained byreducing the data rate of packet data communication connection P1 areallocated to the voice communication connection V6. Similarly, the datarate of a packet data communication connection P2 is reduced from the“full rate” to the “½ rate” in order to establish a packet datacommunication connection P4. Here, communication resources obtained byreducing the data rate of the packet data communication connection P2are allocated to the packet data communication connection P4.

Then, if a new connection is further established, as shown in FIG. 19,the data rates of packet data communication connections are sequentiallyreduced. In this case, if a new packet data communication connection isestablished, the data rate of a connection with the highest data rate isreduced and the same data rate as the lowest data rate of all the datarates of existing packet data communication connections is assigned tothe new connection. If a new connection is further established after thedata rates of all packet data communication connections are reduced tothe lowest speed, the connection is refused. In other words, call lossoccurs.

On the other hand, as described with reference to FIGS. 15 and 16, ifthere is delay in a specific connection, it is checked whether there areavailable communication resources to be additionally allocated to theconnection. If there are available communication resources, thecommunication resources are allocated to the connection, and the datarate of the connection is improved. In the example shown in FIG. 20,communication resources are additionally allocated to packet datacommunication connection P2, and the data rate of the connection isimproved from a “½ rate” to a “full rate”.

If the release of a call generates available communication resources,the released communication resources are allocated, for example, topacket data communications with the lowest data rate. In this way, thedata rate of the connection is improved.

In this way, in the mobile communication system of the secondembodiment, when a trigger, such as the origination of a call, therelease of a call, delay in communications and the like, occurs,communication resources are properly allocated among connections. Inthis way, communication resources can be efficiently used. Theadjustment of a data rate, in other words, the re-allocation ofcommunication resources can be performed independently in each ofupstream and downstream links.

Third Embodiment

As shown in FIG. 21, a mobile station 41 is connected to a networkthrough a base station 51 and a base station control device 61. A radiotransmission path connects the mobile station 41 and base station 51,and a transmission line (an optical fiber, a metal cable or a radiotransmission path) connects the base station device 51 and base stationcontrol device 61. In this system, the communication resources of theradio transmission path and those of the transmission line are managedby the base station 51 and base station control device 61, respectively.

Although transmitting power, a modulator, a spreading code, ademodulator, a decoder and the like are managed as the communicationresources of the radio transmission path, in the following description,attention is focused on the “transmitting power”. The transmitting powerof each connection is proportional to the data rate of the connection.On the other hand, although a band, a frame-offset, a channel ID and thelike are managed as the communication resources of the transmissionline, in the following description, attention is focused on the “band”.

In order to provide high-speed packet data communications, it ispreferable to allocate the maximum possible communication resources tothe connection. Therefore, in FIG. 21, when the mobile station 41attempts to establish a packet data communication connection, the basestation control device 61 and base station 51 attempt to allocate themaximum possible transmission line resources and the maximum possibleradio resources, respectively, to the connection. However, if therespective amounts of these two types of communication resources are notwell balanced, the usability of one type of communication resourcesdegrades. For example, if the base station control device 61 allocatestransmission line resources corresponding to 2 Mbps, and base station 51allocates radio resources corresponding to 1 Mbps, as a result, thetransmission line resources corresponding to 1 Mbps are reserved, butunusable.

Therefore, in the mobile communication system of the third embodiment,the base station 51 and base station control device 61 jointly allocateradio resources and transmission line resources, respectively, to eachconnection. The method for managing communication resources is describedbelow with reference to FIGS. 22 through 29.

FIG. 22 is a sequence chart showing a process for allocatingcommunication resources in the mobile communication system of the thirdembodiment. In this sequence, the base station 51 periodically notifiesthe base station control device 61 of information about radio resources,and the communication resources are allocated based on the notices.

Specifically, the base station 51 notifies the base station controldevice 61 of resource information (2201) in a prescribed cycle (everytime period A) regardless of the establishment/release of a call. Thisresource information (2201) represents available radio resources. Inthis example, “available radio resources=B” is informed. In this way,the base station control device 61 find outs the amount of radioresources allocable to a new connection. On the other hand, the basestation control device 61 manages transmission line resources.Therefore, the base station control device 61 can find out both thetransmission line resources and radio resources allocable to a newconnection.

When the mobile station 41 originates a call in such a state, the basestation 51 detects an origination of a call and notifies the basestation control device 61 of the origination of the call. Upon detectingthe call originating from the mobile station 41, the base stationcontrol device 61 determines an amount of transmission line resource tobe allocated to the call within the range of the “amount of theavailable radio resource” informed by the resource information (2201).Here, the respective dimensions of radio resources and transmission lineresources are different. Therefore, the transmitting power as the radioresources and the bandwidth as the transmission line resources areconverted, for example, to a “data rate” and the “number of unitchannels”, respectively. Then, the bandwidth of a transmission linedetermined by the base station control device 61 is informed to the basestation 51 as a resource allocation request (2202).

Upon receipt of the resource allocation request (2202), the base station51 secures both the transmission line resources and radio resourcesbased on the request. In this case, these two types of resources are thesame each other, if they are respectively converted into data rates.Then, the base station 51 transmits a traffic allocation (2203) to themobile station 41. This traffic allocation (2203) is a message used tonotify the mobile station 41 of the radio resource secured by the basestation 51.

In this way, in the sequence shown in FIG. 22, the amount of availableradio resource is informed to the base station control device 61, andthe radio resources and the transmission line resources are allocatedbased on the notice. Therefore, the allocation of unusable resources canbe avoided.

In the sequence shown in FIG. 22, if there are a plurality of call areoriginated within a cycle where resource information (2201) is informed,an amount of the available radio resource found out by the base stationcontrol device 61 and the actual amount of the available radio resourcedo not match. In the sequence shown in FIG. 23, a process for solvingthis problem is performed.

The base station 51 periodically notifies the base station controldevice 61 of resource information (2301) When the mobile station 41originates a call in this system, the base station control device 61generates a resource allocation request (2302) based on the resourceinformation (2301) and transmits the request to the base station 51.Here, it is assumed that the actual amount of the available radioresource of the base station 51 is “B”, and the amount of thecommunications resource designated by the resource allocation request(2302) is “C(C<B)”. In this case, the base station 51 allocates both“radio resource=C” and “transmission line resource=C” to the new calloriginated by the mobile station 41 and notifies the mobile station 41of a traffic allocation (2303). In this way, the mobile station 41starts communications using “communication resources=C”. As a result,the actual amount of the available radio resource of the base station 51becomes “B−C”.

Then, it is assumed that a mobile station 42 originates a call beforesubsequent resource information is informed to the base station controldevice 61. In this case, the base station control device 61 generates aresource allocation request (2304) based on the resource information(2301) received before allocating communication resources to the mobilestation 41, and transmits the request to the base station 51. Here, itis assumed that an amount of the communications resource designated bythe resource allocation request (2304) is “D(B−C<D)”.

In this case, the base station 51 cannot secure the amount of the radioresource requested by the resource allocation request (2304). Therefore,the base station 51 issues an allocation refusal (2405) to the basestation control device 61. This allocation refusal (2405) includes amessage indicating the current actual amount of the available radioresources of the base station 51. In this example, an “available radioresource amount=B−C” is informed.

Upon receipt of the allocation refusal (2405), the base station controldevice 61 generates a resource allocation request (2306) in response tothe refusal and transmits the request to the base station 51. In thiscase, the amount of the communication resources designated by theresource allocation request (2306) is “B−C”. Then, the base station 51allocates both the “radio resource=B−C” and “transmission lineresource=B−C” to the call originated by the mobile station 42, andnotifies the mobile station 42 of traffic allocation (2307). In thisway, the mobile station 42 starts communications using “communicationresources=B−C”.

Although in the sequences shown in FIGS. 22 and 23, the base station 51spontaneously transmits resource information (2201 and 2301) to the basestation control device 61, the base station control device 61 can alsoperiodically make an inquiry about available radio resources to the basestation 51, as shown in FIGS. 24 and 25. In this case, the base stationcontrol device 61 periodically issues a resource inquiry (2401 and 2501)to the base station 51, and the base station 51 returns correspondingresource information (2402 and 2502). The procedure after that is thesame as that of the sequence described with reference to FIG. 22 or 23.

Although in the sequences shown in FIGS. 22 through 25, a base stationperiodically notifies a base station control device of resourceinformation regardless of the establishment/disconnection of a call, theresource information can also be informed using theestablishment/disconnection of a call as a trigger. The sequence in thecases where resource information is informed using theestablishment/disconnection of a call as a trigger is described belowwith reference to FIGS. 26 through 29.

In the sequence shown in FIG. 26, when the mobile station 41 disconnectsa call, the mobile station 41 issues a call release instruction to thebase station control device 61 through the base station 51. Upon receiptof this instruction, the base station control device 61 returns a callrelease response to the mobile station 41 and issues a call releaserequest to the base station 51. In this way, radio resources between thebase station 51 and the mobile station 41 are released.

Upon receipt of the call release response, the base station controldevice 61 issues a resource release request to the base station 51. Thisresource release request includes an instruction to release transmissionline resources between the base station 51 and base station controldevice 61 that are secured for the mobile station 41. Upon receipt of aresource release response corresponding to the resource release request,the base station control device 61 issues a resource inquiry to the basestation 51 to find out the current amount of the available radioresource. Then, the base station 51 transmits corresponding resourceinformation to the base station control device 61. In this way, the basestation control device 61 can find out the latest resource information(amount of the available radio resource).

In the example shown in FIG. 26, the base station control device 61 mustfurther issue a resource inquiry after issuing the resource releaserequest in order to obtain the resource information. However, in thesequence shown in FIG. 27, no resource inquiry is needed. Specifically,upon receipt of the resource release request, the base station 51releases corresponding communication resources and checks the currentamount of the available radio resource. Then, the base station 51 storesthe result in a resource release response corresponding to the resourcerelease request and returns the response to the base station controldevice 61. In this way, the base station control device 61 can find outthe latest resource information (amount of the available radioresource).

In the sequence shown in FIG. 28, resource information is informed usingan origination of a call from the mobile station 41 as a trigger, andcommunication resources are allocated to the mobile station 41 accordingto the resource information. Specifically, when the mobile station 41originates a call, an call origination request is transmitted to thebase station control device 61 through the base station 51. Upon receiptof the call origination request, the base station control device 61makes an inquiry about resource information (amount of the availableradio resource) to the base station 51. Then, the base station controldevice 61 generates a resource allocation request based on the resourceinformation received from the base station 51, and transmits the requestto the base station 51.

The base station 51 secures communication resources for the mobilestation 41 based on the resource allocation request, and notifies themobile station 41 of the secured radio resources using a trafficallocation message.

In the sequence shown in FIG. 28, the base station control device 61must issue a resource inquiry in order to obtain resource information.However, in the sequence shown in FIG. 29, no resource inquiry isneeded. Specifically, upon receipt of the call origination request fromthe mobile station 41, the base station 51 checks the current resourceinformation (amount of the available radio resource). Then, the basestation 51 attaches the resource information to the call originationrequest and transmits the request to the base station control device 61.In this way, the base station control device 61 can find out the latestresource information (amount of the available radio resource).

Although the mobile communication systems of the first through thirdembodiments are described presuming that CDMA is used in a radiotransmission path, the present invention is not limited to CDMA.

In addition, although in several examples among the first through thirdembodiments, hand-off/rate adjustment is performed using a callorigination from a mobile station accommodated in a base station as atrigger, the present invention is not limited to this trigger. Forexample, hand-off/rate adjustment can also be performed using anincoming call to a mobile station accommodated in a base station as atrigger.

1. A mobile communication system in which a mobile station and a basestation are connected by a radio transmission path, and the base stationand a base station control device are connected by a transmission line,comprising: a first management unit in the base station managing firstdata indicating an amount of available resources of the radiotransmission path defined along a first dimension; a notification unitperiodically notifying the first data from the base station to the basestation control device; a second management unit in the base stationcontrol device managing second data indicating an amount of availableresources of the transmission line defined along a second dimension; aconversion unit in the base station control device for converting thefirst and second data to be defined along a common dimension; adetermination unit in the base station control device determining amaximum available amount of communication resources within both of theconverted first and second data in the common dimension; an allocationunit allocating first communication resources corresponding to themaximum available amount for the radio transmission path and secondcommunication resources corresponding to the maximum available amountfor the transmission line; a detection unit detecting disconnection of acall of the mobile station; a release unit releasing the firstcommunication resources which have been allocated to the released callin response to the disconnection of the call, wherein said notificationunit notifies the base station control device of an updated usage of thefirst communication resources after the release of the call; and aninquiry unit, provided in the base station control device, inquiringabout the updated usage of the first communication resources to the basestation when the disconnection of the call is detected, wherein saidnotification unit performs the notification in response to the inquiryfrom said inquiry unit.
 2. A mobile communication system in which amobile station and a base station are connected by a radio transmissionpath, and the base station and a base station control device areconnected by a transmission line, comprising: a first management unit inthe base station managing first data indicating an amount of availableresources of the radio transmission path defined along a firstdimension; a notification unit periodically notifying the first datafrom the base station to the base station control device; a secondmanagement unit in the base station control device managing second dataindicating an amount of available resources of the transmission linedefined along a second dimension; a conversion unit in the base stationcontrol device for converting the first and second data to be definedalong a common dimension; a determination unit in the base stationcontrol device determining a maximum available amount of communicationresources within both of the converted first and second data in thecommon dimension; an allocation unit allocating first communicationresources corresponding to the maximum available amount for the radiotransmission path and second communication resources corresponding tothe maximum available amount for the transmission line; a detection unitdetecting a call connection request from the mobile station; anacquisition unit acquiring the first communication resources to beallocated to the call in response to the connection request, whereinsaid notification unit notifies the base station control device of anupdated usage of the first communication resources after theacquisition; and an inquiry unit, provided in the base station controldevice, inquiring about the updated usage of the first communicationresources to the base station when the call connection request isdetected, wherein said notification unit performs the notification inresponse to the inquiry from said inquiry unit.